This invention relates to needle/armature assemblies for fuel injectors and more particularly to a needle/armature assembly for a fuel injector with a rotation limiting feature.
The assembly of fuel injectors, in particular, the lift setting, of fuel injectors with an off-center impact point between the armature and inlet tube is believed to be more difficult and time consuming than those fuel injectors designed without an off-center impact point between the armature and inlet tube. The needle/armature assembly of the off-center impact injector appears to demonstrate a tendency to rotate due to the armature and inlet tube surfaces being non-parallel. These off-center impact point injectors have demonstrated to be lift sensitive to the rotational location of the needle/armature assembly relative to the inlet tube. It is believed that this sensitivity is due to the impact surface of the armature and inlet tube being non-parallel. This sensitivity to needle/armature position may result in reduced manufacturer yield of the fuel injector due to failures of the injector with respect to lift and static flow testing. This sensitivity may also contribute to injector lift shift, and resulting flow shift over durability cycling.
It would be beneficial to provide a needle/armature rotational limiting device that overcomes the aforementioned rotational problems in the needle/armatures of offset impact fuel injectors.
Briefly, the present invention provides a solenoid actuated fuel injector with a repeatable stroke. The fuel injector comprises, a housing having a fuel inlet, a fuel outlet, and a fuel passageway extending from the fuel inlet to the fuel outlet along a longitudinal axis. The fuel injector further comprises, a valve body disposed proximate the fuel outlet. The valve body includes an inlet portion and an armature guide eyelet that is disposed in the inlet portion of the valve body within the fuel passageway. The armature guide eyelet is sized to direct and support reciprocal motion of the needle/armature assembly within the fuel passageway along the longitudinal axis.
The solenoid actuated fuel injector also comprises a needle/armature assembly that is reciprocally disposed in and axially aligned with the fuel passageway. The needle/armature assembly includes an upper bearing guide fixedly connected to a needle stem portion. The upper bearing guide comprises a bearing portion and a contacting portion. The armature guide eyelet comprises a first portion that circumscribes the upper bearing guide bearing portion, and a second portion engaging the upper bearing guide contacting portion.
The present invention also provides a method of mechanically insuring a repeatable stroke of a needle/armature assembly within a solenoid actuated fuel injector. The method comprises, providing a housing that includes a fuel inlet, a fuel outlet, and a fuel passageway that extends from the fuel inlet to the fuel outlet along a longitudinal axis. The method further comprises, providing a valve body disposed proximate the fuel outlet. The method additionally comprises, providing a needle/armature assembly reciprocally disposed in and axially aligned with the fuel passageway.
The needle/armature assembly includes an upper bearing guide fixedly connected to a needle stem portion. The method includes, providing an armature guide eyelet disposed in an inlet portion of the valve body within the fuel passageway. The armature guide eyelet is sized to direct and support the reciprocal motion of the needle/armature assembly within the fuel passageway along the longitudinal axis. The method further includes, forming a bearing portion and a contacting portion on the upper bearing guide of the needle/armature assembly. The method also includes, forming a first portion of the armature guide eyelet that circumscribes the upper bearing guide bearing portion and forming a second portion of the armature guide eyelet that abuts the upper bearing guide contacting portion. The method additionally includes, engaging the second portion of the armature guide eyelet and the contacting portion of the upper bearing guide of the needle/armature assembly.
The present invention further provides a method of operating a needle/armature assembly within a solenoid actuated fuel injector. The method comprises actuating reciprocal motion of the needle/armature assembly within a valve body of the solenoid actuated fuel injector. The method further comprises limiting the axial rotation of the needle/armature assembly within the valve body of the solenoid actuated fuel injector.